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RBMK, a Russian acronym translated roughly means "reactor cooled by water and moderated by GRAPHite", is one of the two types of reactors the Soviets have built for the production of nuclear power. The RBMK was developed by the Soviets from earlier model
s that had been used to generate nuclear weapons, as well as produce heat for district heating. [3]
Diagram-1 Layout of Reactors No. 3 & 4 at the Chernobyl Nuclear Power Station. Unit No. 4 is the one that was destroyed in the accident.
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The RBMK-type reactor, like all other nuclear reactors, uses nuclear fission to split nuclei, releasing energy. In order to carry out fission, there must be a bombarding particle, such as a neutron, and a target particle, such as Uraniu
m. When the bombarding particle splits the nucleus in the target particle into two separate and nearly equal parts, nuclear fission releases part of the energy of the nucleus. Some of the energy released is radiation, but most of it ta
kes the form of heat. [4]
If you were to put together blocks of uranium, attempting to split the nuclei, you would find that the neutrons move far too fast giving them a greater chance of missing the uranium atoms altogether. Nuclear power stations therefore use a moderator which slows the neutrons down as they pass through it. United States and Canadian reactors, along with others, use water as the moderator. However, this is not the case in the Soviet RBMK-type reactors, which use solid GRAPHite (a form of carbon), t
he same GRAPHite found in pencils, only purer. [5]
As shown in the illustration above, a nuclear reactor is made up of the following important parts:
 | The Reactor Vessel
 | houses all of the other reactor parts
|
| The Core
| consists of a huge container filled with the GRAPHite blocks (in RBMK reactors)
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| The Control Rods
| long metal rods which, in the Chernobyl reactors, contain boron
| they help control the chain reaction by absorbing free neutrons
| an elevator-like device just outside of the reactor vessel inserts or withdraws the rods to slow down or speed up a chain reaction, respectively
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The operation of a nuclear reactor is as follows:
| as the reaction occurs, the uranium fuel becomes hot
| water pumped through the core in contained pressure tubes removes the heat from the fuel
| the water boils into steam
| the steam turns two turbines which spin electrical generators
| the water is cooled
| | | | |
...and the process continues on and on. All the reactor is really doing is boiling water which in turn, becomes steam and turns turbines to generate electricity. [6]
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